1. Field of the Invention
The present invention relates to a semiconductor device and a method of fabricating th e same. More particularly, this invention relates to a semiconductor device having a film, which reduces the deterioration of the characteristics of the device caused by water or a hydroxyl group and does not affect the initial characteristics of the device, and a method of fabricating the same.
2. Description of the Related Art
There are two conventional methods to reduce the deterioration of the characteristics of a semiconductor device caused by water or a hydroxyl group.
One way is to cover a device with a PE-TEOS (Plasma Enhanced Tetra-Ethyl-Ortho-Silicate) film formed by plasma CVD (Chemical Vapor Deposition), form a BPSG (Boro-Phospho Silicate Glass) film on the PE-TEOS film and form an insulator film on the BPSG film (see K. Machida et al., "TRANSACTIONS OF ELECTRON DEVICES," IEEE, Vol. 41, No. 5, May 1994, pp. 709-714).
The other way is to cover a device with a silicon nitride film formed by LPCVD (Low Pressure Chemical Vapor Deposition) (see Uraoka et al., Shingaku Gihou, SDM 88-42, 1988, pp. 13-18).
In the Machida et al. process, attention was paid to the prevention of the diffusion of water or hydroxyl group into each device from the insulator film on the BPSG film.
When the BPSG film itself is the supply source of water or a hydroxyl group, therefore, the diffusion of water or hydroxyl group cannot be prevented.
The Uraoka et al. process has a great effect of preventing the permeation of water or a hydroxyl group. When a silicon nitride film is formed on an MOSFET (Metal Oxide Semiconductor Field Effect Transistor), however, an increase occurs in the initial short-channel effect or the reliability of the MOSFET. When a silicon nitride film is not formed on the MOSFET, the BT (Bias Temperature) instability increases.